step2.1: rename 64-bit images .MCD -> .MC4 per spec sections 8 and 14

Loader2.mod

@@ -31,7 +31,7 @@ VAR
   buf : ARRAY [0 .. 65535] OF CHAR ;
   f : FIO.File ;
 
-(* Load one translated .MCD image into module `slot`.  The image and its
+(* Load one translated .MC4 image into module `slot`.  The image and its
    zero-filled data window (plus globals) are placed at `next` and `next` is
    advanced past them, so several modules share the arena without overlap
    (multi-window arena).  The requested module lives at MTBL slot `dcnt`,
@@ -154,7 +154,7 @@ BEGIN
     fname [k] := '.' ;
     fname [k + 1] := 'M' ;
     fname [k + 2] := 'C' ;
-    fname [k + 3] := 'D' ;
+    fname [k + 3] := '4' ;
     fname [k + 4] := 0C ;
     LoadOne (j - 1, fname, next, FALSE) ;
   END ;

MC64.mod

@@ -8,7 +8,7 @@ FROM Console IMPORT WriteString, WriteLn ;
 BEGIN
   Init () ;
   InitModuleTable () ;
-  Call ("boot.mc4") ;
+  Call ("boot.MC4") ;
   WriteString ("[vm end]") ;
   WriteLn ;
 END MC64.

SESSION.md

@@ -32,6 +32,6 @@ Why stopped: the 64-bit loader binds ONE module window into slot 0 and hard-fenc
   (NOT the foreign FIO.o used in a lost earlier glob). Build rc != 0 => stop, restore.
 
 ## Regression that stayed green (from earlier verified runs this tree)
-  Stack.MCD -> trans8to64 -> Stack64.MCD -> mcint : rc=0
+  Stack.MCD -> trans8to64 -> Stack64.MC4 -> mcint : rc=0
   9-spec translator regression: Stack, Array, Local, Extended, Instruction, Loader,
   Console, FileIO, MCODE-stub: 8 ok / 1 skip (the translator never regresses these).

docs/mc64-spec.md

@@ -790,7 +790,7 @@ source relies on.
   `UnixArgs`, …). Vendor `m2pim` modules fail to link against `-fiso` objects.
 - `System.ProgramArgs.ArgChan` is **not usable** in this gm2 build: `TextRead` on it
   blocks forever and `Look` returns a `'.'` filler instead of `endOfInput`. The VM
-  therefore boots a fixed `boot.mc4` (generated by `mkdemo`) instead of parsing argv.
+  therefore boots a fixed `boot.MC4` (generated by `mkdemo`) instead of parsing argv.
 - File I/O uses `StreamFile.Open/Close` + `IOChan.RawRead/RawWrite` (`ChanConsts`
   `FlagSet{readFlag, oldFlag, rawFlag}` / `{writeFlag, rawFlag}`).
 - Screens output writes go to the ISO standard output channel

docs/session-summary.md

@@ -9,9 +9,9 @@ Constraints honored so far: no analysis/disassembly of `.MCD` binaries — work
 - `M2compiler/mc64/` — all VM code:
   `Memory, Local, Stack, Console, FileIO, Global, Instruction, Extended, Interpreter,
   Loader2` (.def + .mod);
-  programs `MC64.mod` (REPL harness), `mkdemo.mod` (`boot.mc4`), `mcint.mod`
-  (`mcint file.MCD` launcher), `mkdtest.mod` (`example.MCD` generator);
-  built: `mkdemo`, `mc64`, `mcint`, `mkdtest`, `boot.mc4`, `example.MCD`.
+  programs `MC64.mod` (REPL harness), `mkdemo.mod` (`boot.MC4`), `mcint.mod`
+  (`mcint file.MC4` launcher), `mkdtest.mod` (`example.MC4` generator);
+  built: `mkdemo`, `mc64`, `mcint`, `mkdtest`, `boot.MC4`, `example.MC4`.
 - `M2compiler/mc64-spec.md` — normative spec (§5.2 frames, §7.1 descriptor layout,
   §8.3 checksum rule, §9.3 SYSTEM ABI, §10 0x12/0x40 sub-dispatches, §11 opcode table,
   §12 switch/strings, §16 GNU-M2 ISO implementation notes).
@@ -34,10 +34,10 @@ gm2 -fiso -o mkdtest mkdtest.mod FileIO.o Console.o
 ```
 
 ## Verification status (all green)
-- `./mkdemo` -> `boot.mc4` ; `./mc64` -> `Hello MC64!` + `[vm end]` (0) ;
-  `./mcint boot.mc4` -> `Hello MC64!` (0) ; `./mcint` -> usage (0) ;
-  `./mcint nope.MCD` -> Fatal (1).
-- `./mkdtest` -> `example.MCD` (1350 B, MC64 format) ; `./mcint example.MCD` — 24/24
+- `./mkdemo` -> `boot.MC4` ; `./mc64` -> `Hello MC64!` + `[vm end]` (0) ;
+  `./mcint boot.MC4` -> `Hello MC64!` (0) ; `./mcint` -> usage (0) ;
+  `./mcint nope.MC4` -> Fatal (1).
+- `./mkdtest` -> `example.MC4` (1350 B, MC64 format) ; `./mcint example.MC4` — 24/24
   opcode-checks pass (exit 0):
   loop g:=2g+1 x10 = 2047; add/sub/mul/div/mod; bit_and/or/xor & power2;
   extended 0x40: drop, uc_add, uc_mul, uc_div, uc_mod, long_negate, build_field_mask;
@@ -45,12 +45,12 @@ gm2 -fiso -o mkdtest mkdtest.mod FileIO.o Console.o
   copy_block -> "abc"; global/local_dw load/store; load_global_dw;
   forward jp_fwd; jpfalse_back loops; proc_call into decimal `print_num`
   (enter/fct_leave, load_param, reserve, udiv/umod, store_indexed_byte).
-  - `./mkread` -> `readtest.MCD` (453 B) ; `./mcint readtest.MCD` — SYSTEM service 2
-  reads stdin lines: `printf 'first line\nsecond line\n' | ./mcint readtest.MCD`
+  - `./mkread` -> `readtest.MC4` (453 B) ; `./mcint readtest.MC4` — SYSTEM service 2
+  reads stdin lines: `printf 'first line\nsecond line\n' | ./mcint readtest.MC4`
   echoes `you said: first line` then `again: second line` (0). Edge cases verified:
   EOF without trailing newline still echoes; empty line -> count 0; immediate EOF -> 0;
   two consecutive reads prove the line mark is consumed (Skip) so the next read starts fresh.
-- `./mcint boot.mc4` -> `Hello MC64!` (0) ; `./mcint example.MCD` — 24/24 (0).
+- `./mcint boot.MC4` -> `Hello MC64!` (0) ; `./mcint example.MC4` — 24/24 (0).
 - Public-dollar checks: `::` VM accepts THE-SPEC–conformant images only.
 
 ## Key technical facts learned
@@ -89,13 +89,13 @@ gm2 -fiso -o mkdtest mkdtest.mod FileIO.o Console.o
 - SYSTEM service 2 (read line) implemented via ISO `StdChans.StdInChan` +
   `IOChan.Look/Skip` char loop (avoids `TextRead`'s "current line" blocking);
   stores chars up to (not incl.) line mark or EOF, NUL-terminates, pushes byte count.
-  Documented in spec §9.3; readtest.MCD exercises it.
+  Documented in spec §9.3; readtest.MC4 exercises it.
 
 ## Current task state
-- Writing an **MCD example file** to exercise the interpreter: **DONE** —
-  `mkdtest.mod` -> `example.MCD`, 24 opcode-checks pass under `./mcint`.
+- Writing an **MC4 example file** to exercise the interpreter: **DONE** —
+  `mkdtest.mod` -> `example.MC4`, 24 opcode-checks pass under `./mcint`.
 - **stdin support for SYSTEM service 2**: **DONE** — implemented in `Interpreter.mod`
-  (`ReadLine`), `mc64-spec.md` §9.3 updated, `mkread.mod` -> `readtest.MCD` proves
+  (`ReadLine`), `mc64-spec.md` §9.3 updated, `mkread.mod` -> `readtest.MC4` proves
   line reads + line-mark consumption under piped input.
 
 ## Next steps / open ideas

mcint.mod

@@ -1,7 +1,7 @@
 MODULE mcint ;
 
 (* Standalone launcher for the MC64 interpreter.
-   usage: mcint module.MCD
+   usage: mcint module.MC4
    The first program argument is treated as the module file to boot. *)
 
 FROM Loader2 IMPORT Call ;
@@ -14,7 +14,7 @@ VAR
 
 PROCEDURE Usage ;
 BEGIN
-  WriteString ("usage: mcint module.MCD") ;
+  WriteString ("usage: mcint module.MC4") ;
   WriteLn ;
 END Usage ;
 

mkdemo.mod

@@ -1,6 +1,6 @@
 MODULE mkdemo ;
 
-(* Generates boot.mc4, a single-module MC64 image that prints
+(* Generates boot.MC4, a single-module MC64 image that prints
    "Hello MC64!" via the SYSTEM write-string service (§9.3). *)
 
 FROM FileIO IMPORT WriteFile ;
@@ -102,7 +102,7 @@ BEGIN
   END ;
   Put32 (HeaderSize + DescChecksum, sum) ;
 
-  IF NOT WriteFile ("boot.mc4", buf, FileSize) THEN
-    Fatal ("mkdemo: cannot write boot.mc4") ;
+  IF NOT WriteFile ("boot.MC4", buf, FileSize) THEN
+    Fatal ("mkdemo: cannot write boot.MC4") ;
   END ;
 END mkdemo.

mkdep.mod

@@ -1,12 +1,12 @@
 MODULE mkdep ;
 
 (* Synthetic two-module MC64 test for the Loader2 dep-chain :
-   - STAK.MCD : dependency-free sidecar.  proc0 = empty TOINIT,
+   - STAK.MC4 : dependency-free sidecar.  proc0 = empty TOINIT,
      proc1 = writes a host string (proves an extern call reached
      the dependency's code via MTBL slot 0 + cross-module call/leave).
-   - DEP.MCD  : main module, dcnt=1, dep name "STAK".  TOINIT
+   - DEP.MC4  : main module, dcnt=1, dep name "STAK".  TOINIT
      extern-calls STAK.proc1, then end_program.
-   Run : mkdep ; then  mcint DEP.MCD   from the dir holding STAK.MCD.
+   Run : mkdep ; then  mcint DEP.MC4   from the dir holding STAK.MC4.
    Expect one line from the STAK proc, exit 0. *)
 
 FROM FileIO IMPORT WriteFile ;
@@ -137,12 +137,12 @@ BEGIN
   END ;
   Put32 (HeaderSize + DescChecksum, sum) ;
 
-  IF NOT WriteFile ("STAK.MCD", buf, HeaderSize + pcimg) THEN
-    Fatal ("mkdep: cannot write STAK.MCD") ;
+  IF NOT WriteFile ("STAK.MC4", buf, HeaderSize + pcimg) THEN
+    Fatal ("mkdep: cannot write STAK.MC4") ;
   END ;
 END Stak ;
 
-PROCEDURE Dep ;  (* build DEP.MCD *)
+PROCEDURE Dep ;  (* build DEP.MC4 *)
 VAR st0, dep : CARDINAL ;
 BEGIN
   which := tDep ;
@@ -188,8 +188,8 @@ BEGIN
   END ;
   Put32 (HeaderSize + DescChecksum, sum) ;
 
-  IF NOT WriteFile ("DEP.MCD", buf, HeaderSize + pcimg) THEN
-    Fatal ("mkdep: cannot write DEP.MCD") ;
+  IF NOT WriteFile ("DEP.MC4", buf, HeaderSize + pcimg) THEN
+    Fatal ("mkdep: cannot write DEP.MC4") ;
   END ;
 END Dep ;
 

mkdtest.mod

@@ -1,7 +1,7 @@
 MODULE mkdtest ;
 
-(* Generates example.MCD, a single-module MC64 image that exercises far
-   more of the interpreter than boot.mc4 :
+(* Generates example.MC4, a single-module MC64 image that exercises far
+   more of the interpreter than boot.MC4 :
 
      proc0 (TOINIT, main) :
        - a CARDINAL do-while loop  g := g*2+1  (10 iterations)  -> 2047
@@ -341,7 +341,7 @@ BEGIN
   END ;
   Put32 (HeaderSize + DescChecksum, sum) ;
 
-  IF NOT WriteFile ("example.MCD", buf, HeaderSize + pcimg) THEN
-    Fatal ("mkdtest: cannot write example.MCD") ;
+  IF NOT WriteFile ("example.MC4", buf, HeaderSize + pcimg) THEN
+    Fatal ("mkdtest: cannot write example.MC4") ;
   END ;
 END mkdtest.

mkread.mod

@@ -1,6 +1,6 @@
 MODULE mkread ;
 
-(* Generates readtest.MCD, a single-module MC64 image that reads two lines
+(* Generates readtest.MC4, a single-module MC64 image that reads two lines
    from the host standard input via SYSTEM service 2 and echoes both back:
 
      reserve 128 bytes  ; store_global 1        ; input buffer
@@ -139,7 +139,7 @@ BEGIN
   END ;
   Put32 (HeaderSize + DescChecksum, sum) ;
 
-  IF NOT WriteFile ("readtest.MCD", buf, HeaderSize + ilen) THEN
-    Fatal ("mkread: cannot write readtest.MCD") ;
+  IF NOT WriteFile ("readtest.MC4", buf, HeaderSize + ilen) THEN
+    Fatal ("mkread: cannot write readtest.MC4") ;
   END ;
 END mkread.

trans8to64.mod

@@ -1,7 +1,7 @@
 MODULE trans8to64 ;
 
 (* trans8to64 : translate a classic 16-bit Turbo Modula-2 .MCD binary
-   into a 64-bit MC64 .MCD image that mcint can boot.
+   into a 64-bit MC64 .MC4 image that mcint can boot.
 
    16-bit file layout (little-endian) ::
       header   : 16 bytes
@@ -329,7 +329,7 @@ END AddEnt ;
 
 PROCEDURE Usage ;
 BEGIN
-  WriteString ("usage: trans8to64 in.MCD out.MCD") ;
+  WriteString ("usage: trans8to64 in.MCD out.MC4") ;
   WriteLn ;
 END Usage ;